Rural Southeast Texas Air Quality Measurements during the 2006 Texas Air Quality Study

Abstract

The authors conducted air quality measurements of the criteria pollutants carbon monoxide, nitrogen oxides, and ozone together with meteorological measurements at a park site southeast of College Station, TX, during the 2006 Texas Air Quality Study II (TexAQS). Ozone, a primary focus of the measurements, was above 80 ppb during 3 days and above 75 ppb during additional 8 days in summer 2006, suggestive of possible violations of the ozone National Ambient Air Quality Standard (NAAQS) in this area. In concordance with other air quality measurements during the TexAQS II, elevated ozone mixing ratios coincided with northerly flows during days after cold front passages. Ozone background during these days was as high as 80 ppb, whereas southerly air flows generally provided for an ozone background lower than 40 ppb. Back trajectory analysis shows that local ozone mixing ratios can also be strongly affected by the Houston urban pollution plume, leading to late afternoon ozone increases of as high as 50 ppb above background under favorable transport conditions. The trajectory analysis also shows that ozone background increases steadily the longer a southern air mass resides over Texas after entering from the Gulf of Mexico. In light of these and other TexAQS findings, it appears that ozone air quality is affected throughout east Texas by both long-range and regional ozone transport, and that improvements therefore will require at least a regionally oriented instead of the current locally oriented ozone precursor reduction policies. IMPLICATIONS Ozone National Ambient Air Quality Standard (NAAQS) violations in the two major Texas metropolitan areas have been occurring for decades. Recent data show that high ozone concentrations in east Texas are not limited to the Houston and Dallas/Fort Worth areas, but can be transported far downwind, possibly leading to NAAQS violations in rural areas. This paper provides an assessment of rural ozone concentrations in Brazos County, 120 km northwest of Houston during summer 2006, showing that this area likely violated the NAAQS, in part due to long-range transport importing high ozone background concentrations, in part due to impacts of the Houston pollution plume under southeast wind directions. © 2011 Air & Waste Management Association.